Field of the Invention
The present invention generally relates to semiconductor devices, and more particularly to a metal-insulator-metal (MIM) capacitor for use in back-end-of-the-line (BEOL) structures.
In the semiconductor industry, high performance capacitors are in great demand since such capacitors are essential for numerous applications, including, for example, RF and microwave. High performance capacitors have greater densities than a conventional capacitor, which leads to a reduction in chip size.
Metal-insulator-metal (MIM) capacitors that are formed above back-end-of-the line (BEOL) metallurgy are also known. A typical MIM capacitor for use in BEOL structures is shown, for example, in FIG. 1. Specifically, FIG. 1 illustrates a prior art MIM capacitor which includes a SiO2 or SiN dielectric layer 12 sandwiched between bottom conductive electrode 10 and top conductive electrode 14. In order to increase the capacitance density of prior art MIM capacitors, there has been a desire to replace the SiO2 or SiN dielectric film with a high dielectric constant film such as Ta2O5.
However, MIM capacitors containing a high dielectric constant film have the following problems associated therewith: (i) oxygen diffuses readily to the metal-insulator interface through the bottom electrode during deposition of the dielectric film; and (ii) BEOL thermal cycles, such as interlayer dielectric deposition and H2 sintering, lead to increased leakage current and possible shorting of the MIM structure due to the high dielectric constant film reacting with the MIM's conductive electrodes. The aforesaid problems are particularly relevant when Ta2O5 is used as the high dielectric constant film.
Despite the problems associated with prior art MIM capacitors containing a high dielectric constant film, there is continued interest in developing MIM capacitors which include a high dielectric constant material, such as Ta2O5 (k˜25), yet do not exhibit any of the problems mentioned hereinabove.